Improved direction finder balancer



31, i935. l B. DOLBEAR 2,026,123

IMFRQVED DIRECTION FINDER BALANCER Filed Jan. 18, 1952 ATTORNEY Patented Dec. 31, 1935 UNITED STATES IMPROVED vrnlnno'rl'o'iii FINDER. BALANCER' Benjamin L. Dolbear, Belmont, Mass., assignor to Radio Corporation of America, a corporation of Delaware Application January 18, 1932,V Serial No. 587,325

6 Claims.

This invention relates to improved radio direction finder balancers, and more particularly those used in the higher frequency circuits.

An object of this invention is to simplify and improve direction finder balancers.

A further object of this invention is to simplify and so arrange the devices which are associated With a capacity balancer that the maximum efflciency may be obtained when using such an ar- 10' rangement of parts in the higher frequency direction finder circuit. Likewise, such an arrangement also results in a minimum'number of essential parts and thereby reduces the cost of manufacture of such devices. Y

A feature of this invention is the combining of a sense resistance and a capacity balancer and by an arrangement of a pair of contacts in such a manner that the rotaryY plate, which is an importantelement to this invention, may actuate the contacts mentioned above and thereby place the sense resistance in series with one side of a loop when desired to determine the sense of direction from which a signal is coming.

It is well known in the art of direction nding that voltages induced in the loop from sources other than theA distant radio transmitter, such as the transmitter energy picked up and reradiated from nearby wires or any other conducting objects produce the same effect as unbalanced symmetry of the loop receiving circuit. Such unbalance or distortion prevents the operator of a direction finder from obtaining a well defined and sharp minimum or null point. Therefore, to improve the minimum a capacity balancer is connected to each side of the loop to' balance out any dissymmetry occurring when the loop is rotated. I have found that in a radio direction finder employing the higher frequencies in the order of 1500 to 30,000 kilocycles or short wave lengths, that it is desirable and often necessary to shorten and prevent sharp bends in the leads or wires connecting the plates of a capacity balancer with those of the sense resistance and its associated sense switch. I therefore reduce in number and shorten the wires connecting the loop and the balancer,

and also those of the sense resistance, by assembling the sense resistance and the sense switch on a single insulating member. I further arrange the contacts of the senseswitch in such a manner that the operating knob of the capacity balancer also serves to operate the sense switch. I am so able to arrange these latter parts for the reason that the capacity balancer is not used when Van A indication o f the sense of direction of the received 55 signal is to be obtained.

Fig. 4 is a partial direction finder circuit show- 10k ing that portion which relates to' this invention.

The simplified and improved direction finder balancer is shown in Figs. 1, 2 and 3, wherein the base I is of bakelite dilector or other good insulating material of low dielectric loss. Mount- 15 ed upon this base is a central bearing' or bushing 2 which is held in position by the bearing `nut 3. An operating shaft 4 is provided with an insulatedknob, 5, and a pointer 6, and locked to the shaft by means of members 'I6 an-d 'I'I.V 0n the 20 opposite end of the shaft 4 is mounted a single rotary condenser plate 'I which is held securely in position by means of a nut 8, a collar 9, and rivets I0, Il, I2 and I3. A springlIZ provides proper friction for the shaft. Directly below the 25 rotary plate l, but spaced about one thirty-second of an inch, there are located two fixed plates @Li and I5 respectively, each of whichare of equal area and spaced an equal distance from the center of the rotor shaft 4'so that the ca- 30 pacity of each plate will be approximately the same Vwith respect to the center ofthe rotary plate 'I when it is in a horizontal position. TheseV fixed plates I4 and I5 are securedtothe base I by means of metallic supports I6, Il, I8 andIB, 35

and fastened by means' of screws 20, 2|, 22, 23, 4, 25, 26 and 2l. A fie'xiblelead 28 is Vsecuredto the rotar-y plate shaft which in turn connects by means of a backstop spring member VI5 tothe `sense switch contact 29. -A'relativly short con- 40 necting strip 30 connects the contact29 with the terminal screw 3|, Vwasher-aridnut 32 and 33. The other contact 34 of the sense switch is connccted by means of a strip 35 to a clip 36, pro-'- viding the mounting of the sense resistance 341. 45 K The other sense resistance clip 378 isY connected to the xed condenser plate I5 by a lead 40 and thence byV another lead VIII to the terminal screws 42,k washers 43, and nuts 44. lThe other 1 fixed plate I4 is connected from the screw 422 50 by meanrsof'a lead 45. to the terminal screw 4 6., washer 4l, and nutI 48. The base I is' further provided withrsuitable apertures 49, 50, '5I 52, for mounting thejdevice on the panel ofthe direction finder receiving apparatus.l

Cil

Referring now to Fig. 4, a wiring diagram of this device is enclosed within the dot and dash line, also the external parts of the circuit are included, which have not been previously mentioned. There is shown a loop 53, grounding condenser 54, ground 55, sense antenna 5B, tuning condenser 51, vacuum tubes 58 and 59, with input grids 60 and 6l, filaments G2 and 63,'with lament rheostat 64, and battery 65 which indicate the filament supply for the vacuum tubes 58 and 59, plates 66 and 61 which form the input of a `superheterodyne receiver 13 comprising a local oscillator 14, rst and second detectors 68 and 69 respectively, and a sufficient audio stage 19 to Igive the desired phones 1l. t

In the operation of this improved balancer the operator first sets the pointer on zero, which is a position wherein each of the xed plates I4 and l5 are covered by the rotary-'plate 1 by substantiallycan equal area. Then assuming a beacon station is being received, by listening in the phones 1I he carefully sets the loop 53 at a position of minimum signal response. VThe knob 5 is then rotated slowly in each direction until a position .is found that will Yfurther reduce the strength of the signal. It then may be necessary for him to obtain a more accurate setting by slight readjustment vof the loop and then again the balancer. This position will be the line position of the received signal, and unless the operator knows the approximate source of the signal in respect Vto his position, he Will next nd it necessary to determine whether the signal is ahead yofor behind him. Therefore,Y with the loop remaining in the position of minimum signal response mentioned above, the operating knob 5 is rotated as far as possible, toward the contact 29. In this position the rotary plate 1Y will close the contacts 29 and 34 and in such a po- Vsition the sense resistance 31 is then placed in series with the sense antenna and .one side of the loop 53. The loop is then rotated through 90 degrees from the null point and rthe operator thennotes whether the signal increases or designal strength for the creases in strength. The position of increased.

pair of oppositely disposedxed plates, a plu-` rality of Yupwardly extended support posts for supporting said pair of fixed plates'which are connected to one side of said loop and are oppositely disposed in respect to the shaft of said rotary plate, a pair of upward extending-spring contact members having relatively fixed and movable contacts, the movable contact electrically connected to said sense antenna and the rotary plate and being arranged on the base at right angles to each of said xed plates and positioned in the path of said rotary plateso as to make electrical connection to the relatively fixed contact when the rotary plate is rotated past the `position beyond the active capacity area ofat least one of thexed plates to close the contacts and to electrically connect said sense antenna in series with said resistance which is electrically connected on one end to said fixed contact and on the other end to one side of the loop to indicate the sense of direction of an incoming wave.

2. In a radio direction'finder capacity balancer for an open and closed antenna system comprising a loop antenna, a sense antenna, said capacity balancer having a fixed plate electrode connected to each side of said loop antenna, said capacity balancer having mounted on a common base a rotary plate having a central shaft, said xed plate electrodes oppositely disposed in respect to the shaft of said rotary plate, a pair of spring members having relatively nxed and movable contacts, the movable contact being electrically connected to the rotary plate and posi- Ytioned adjacent said shaft to make an electrical connection with the relatively xed contact by means of the edge of Vsaid rotary plate moving the movablecontact toward said relativelyfixed contact when saidY rotary plate is rotated in a position'beyondthe area of at least one of the fixed plates soV as to electrically connect said sense antenna Vin series with a resistance which is electrically connected on one end to said xed contact and to one of said fixedplates on the other end so as to be connected in series with one side of said loop to indicate the sense of direction of an incoming wave when said contacts are closed.

3. In anni-lateral receiving circuit comprising an open antenna, a closed antenna, said closed antenna having in'combination a capacity balancercornprising a'rotary plate and a pair of oppositely disposed xed plates, a switch having relatively fixed andmovable contacts `and a resistance mounted on a base, one side of said resistance being electrically connected to at least one of said fixed plates and said closed antenna, each side of said closed antenna electrically connected to one of the oppositely disposed fixed plates, said rotary plate being electrically connected to said relatively fixed contactand said open antenna, means for electrically connecting the otherside of said resistance to one side of said lmovable contact by means Vof the edge of said rotary plate moving said movable contact toward said relatively fixed contact so that the resistance and said open antenna are connected in series with one-side of said closed antenna to indicate the senseof vdirection of the received energy.

trical contacts, atleast one of said contacts being connectedto one side of said resistance, the other side of said resistance being connected to one of said fixed plates Vand said iixed contact member, said other contact being positively connected .toY said rotary plate and intermittently to said openantenna by means of said rotary plate moving in a path so as to close said contacts for electrically connecting in series said open antenna with one side of s'aid loop, for indicating the sense of direction of an incoming wave.

5. A uni-lateral receiving energy responsive circuit comprising a closed antenna and an open antenna, said closed antenna forming a circuit, a

resistance and a switch, said switch having xed l and movable contacts, a pair of xed condenser plates substantially of the same area, each of said fixed plates being connected to one side of said closed antenna, and a rotary plate connected to the open antenna circuit and to said movable contact on said switch, the fixed contact of said switch being connected to one side of said resistance, the other side of said resistance being connected to at least one of said xed plates, means for closing said contacts to provide connections to one side of said closed antenna, the resistance and said xed contact for placing said resistance in series with said open antenna cirs cuit When said plate is rotated to an unbalanced position in which said rotary plate substantially covers only the area of one of said fixed plates to indicate the sense of direction of energy response.

6. In a radio direction nder comprising a sense antenna, a loop, a capacity balancer having a base` on which is mounted a rotary plate, a resistance, apair of oppositely disposed xed plates, said xed plates being connected to each side of said loop and are oppositely disposed in respect to the center of said rotary plate, a pair of contact members one of which is electrically connected to said sense antenna and the rotary plate and arranged on the base at right angles to each of said xed plates and positioned in the path of said rotary plate so as to make electrical connection by closing said contacts when the rotary plate is rotated past the position beyond the active capacity area of at least one of the xed plates to electrically connect said sense antenna in series with said resistance which is electrically connected to one of said contacts, and the other end oi said resistance being connected with one side of said loopto indicate the said rotary plate closes said contacts.

BENJAMIN L. DOLBEAR. 

